In a device where a particularly low error rate is desired, ATPG (Automatic Test Pattern Generation) or LBIST (Logic Built In Self Test) techniques may be used to test the device for errors. In some cases, ATPG and LBIST techniques may be used on the same device.
ATPG is an electronic design automation methodology used to find an input (or test) sequence that, when applied to a digital circuit such as an integrated circuit, enables automatic test equipment (ATE) to distinguish between correct circuit behavior and faulty circuit behavior caused by fabrication defects. The generated patterns are used to test devices after manufacture, or to assist with failure analysis.
LBIST circuitry is a form of built in self-test in which hardware is built into integrated circuits allowing them to test their own operation, as opposed to reliance on external automated test equipment. LBIST circuitry relies on the generation of deterministic pseudorandom test patterns used to test integrated circuits, such as when powered on.
Both ATPG and LBIST techniques rely on a generated test clock for use in testing operations. If the generated test clock is missing pulses, then the results of the LBIST or ATPG testing may be incorrect and the test circuitry may malfunction.
Accordingly, development of testing circuits capable of checking the generated test clock for missed clock pulses is needed.